barrage dam
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A barrage is a type of low-head, diversion
dam A dam is a barrier that stops or restricts the flow of surface water An example of surface water is Lake Kinney. Surface water is water Water is an Inorganic compound, inorganic, Transparency and translucency, transparent, tast ...

dam
which consists of a number of large gates that can be opened or closed to control the amount of water passing through. This allows the structure to regulate and stabilize river water elevation upstream for use in irrigation and other systems. The gates are set between flanking piers which are responsible for supporting the water load of the pool created. The term '' barrage'' is borrowed from the
French
French
word "barrer" meaning "to bar".


Dam construction

Dams are made around the world for many different reasons and have a variety of uses. There is a lot to consider when constructing a new dam. The location must be inspected, the purpose of the dam has to pass certain criteria and the effects of possibly removing the dam must also be taken into account. Barrage dams in specific are a form of dam that has a series of gates that control the amount of water passing through it. A barrage dam can be used to divert water for irrigation needs or limit the amount of water down-stream. In most cases, a barrage dam is built near the mouth of the river. The site of dam construction needs to be thoroughly investigated to ensure that the foundation is strong enough to support the dam and has low possibility of failing. When dams are created, they are given a safety rating depending on the type of dam, location, and the possible effects in case of failure. The ratings are from one to five, five having the highest danger rating. The rating of five would be given to dams built with a town or city downstream that would have higher possibility of injury to people in the case of dam failure. New designs have been made that are able to sustain greater amounts of water. An improved wedge-shaped block technology was developed by Rafael Moran and Miguel Toledo. The new structure is able to withstand severe
flooding Flash flooding caused by heavy rain falling in a short amount of time. A flood is an overflow of water that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide ...

flooding
and use less materials, reducing the production cost. Not only could this design save money, but it also can save lives and would increase the safety rating.


Environmental impacts

Dam construction comes with several impacts that can affect the
economy An economy (; ) is an area of the production Production may be: Economics and business * Production (economics) * Production, the act of manufacturing goods * Production, in the outline of industrial organization, the act of making products ( ...

economy
and the
environment Environment most often refers to: __NOTOC__ * Natural environment, all living and non-living things occurring naturally * Biophysical environment, the physical and biological factors along with their chemical interactions that affect an organism or ...
. In specific, there are several ways in which the environment can be affected from dam construction.
Species richness File:Global Amphibian Richness Grids, 2015 Release, All Amphibians (28794889801).jpg, 300px, Global amphibian richness (2015) Species richness is the number of different species represented in an community (ecology), ecological community, landscape ...
is usually measured to determine the effect of a dam on the
ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...

ecosystem
s surrounding dams. To observe the species richness, scientists collect data on the fish and animal populations before and after construction of the dam. With that data, they are able to see how the population size increased or decreased. In some cases, it was found that the species richness was less downstream from a dam compared to further upstream. Inhibiting the volume of water was shown to be detrimental to species diversity and richness. Also, at the entrance of dams, there is less nutrients due to the high-water flow reducing the ecosystems reproduction standard. Along with the species richness, plankton diversity can be an indicator of the ecosystems ability to handle the newly built dam. It has been shown that dams can have an effect on the
migration Migration, migratory, or migrate may refer to: Human migration * Human migration, physical movement by humans from one region to another ** International migration, when peoples cross state boundaries and stay in the host state for some minimum len ...
of fish leading to less reproduction. There are many small factors that can have relatively large impacts that effect the river ecosystems, such as the species richness, volume of water and nutrient levels. Different experiments have been done that look into each of these individually and were able to determine why some dams cause such impacts. While there is substantial evidence and case studies that point to dam construction having environmental impacts, there are also studies that show less damage than expected. Looking at plankton near some dams has shown that plankton are able to continue to live although changes to their habitats. Changes such as the
pH
pH
levels near dams have been recorded and plankton were minimally affected. Other species, however, such as trout, are more affected due to the physical dam inhibiting their migration and reproduction paths. Barrage dams control the amount of water going through them, leading to differences in the amount of water up and downstream from the dam. This discrepancy has different effects on different species native to the area. While there can be reduced flow downstream, there can also be problems upstream. Dams can have buildup of pressure that fish are not accustomed to and they migrate further upstream causing that part of the river to have reduced population sizes. Although there are environmental impacts that come with building new dams, there are also many economies that benefit from a dam. Without dams, it would be much harder to farm and grow livestock. The irrigation technology that comes with building a dam can exceed the risk factor.


Terminology

According to the
World Commission on Dams The World Commission on Dams (WCD) existed between April 1997 and 2001, to research the environmental, social and economic impacts of the development of large dam, dams globally. The self-styled WCD consisted of members of civil society, academia ...
, a key difference between a barrage and a dam is that a dam is built for water storage in a
reservoir A reservoir (; from French French (french: français(e), link=no) may refer to: * Something of, from, or related to France France (), officially the French Republic (french: link=no, République française), is a country primarily loca ...

reservoir
, which raises the level of water significantly. A barrage is built for diverting water, and raises the water level by only a few feet. The latter is generally built on flat terrain across wide, often
meander A meander is one of a series of regular sinuous curves in the channel of a river or other watercourse. It is produced as a watercourse the s of an outer, concave bank () and deposits sediments on an inner, convex bank which is typically a . Th ...

meander
ing rivers. Similar distinctions are used in Egypt, where it is noted: "In this system a "dam" is a structure that forms a reservoir for the storage of water during the annual flood period of the Nile in order to supplement the natural flow of the river during the low-water period; a "barrage" merely raises the river or canal level, when necessary, to the height required for adequate flow into the canals that take off above it.Raye R. Platt, Mohammed Bahy Hefny,
Egypt: A Compendium
p.198,
American Geographical Society The American Geographical Society (AGS) is an organization of professional geographer A geographer is a physical scientist, social scientist or humanist whose area of study is geography Geography (from Greek: , ''geographia'', liter ...
, 1958. Retrieved 2014-12-03
Barrages are usually larger than the
headworks Headworks is a civil engineering term for any structure at the head or diversion point of a waterway. It is smaller than a barrage and is used to divert water from a river into a canal or from a large canal into a smaller canal. at Web archive Hi ...
of irrigation and navigation canals, with which they are associated. Barrages that are commonly used to dam a lagoon or estuary as a method to capture
tidal power#REDIRECT Tidal power Tidal power or tidal energy is harnessed by converting energy from tide (U.S.), low tide occurs roughly at moonrise and high tide with a high Moon, corresponding to the simple gravity model of two tidal bulges; at most ...
from tidal inflows are known as
tidal barrage A tidal barrage is a dam-like structure used to capture the energy from masses of water moving in and out of a bay or river due to tides, tidal forces. Instead of damming water on one side like a conventional dam, a tidal barrage allows water to fl ...
s.


Etymology

The English usage of the term ''barrage'' originates from the
Delta Barrage The Delta Barrage is barrage-type dam that was constructed intermittently beginning in 1833 to its initial completion in 1862. Its purpose was to improve irrigation and navigation along the main Rosetta Rosetta or Rashid (; ar, رشيد ' ; f ...
across the
Nile The Nile, , Bohairic , lg, Kiira , Nobiin Nobiin, or Mahas, is a Northern Nubian languages, Nubian language of the Nilo-Saharan languages, Nilo-Saharan language family. "Nobiin" is the genitive case, genitive form of ''Nòòbíí'' ("Nubi ...

Nile
-branches north of Cairo, built between 1833 and 1862 by the French Linant de Bellefonds and Eugène Mougel employed in the Egyptian Public Works Department, with assistance from , and with the blessing of the Egyptian Viceroy of the
Ottoman Empire The Ottoman Empire (; ', ; or '; )info page on bookat Martin Luther University) // CITED: p. 36 (PDF p. 38/338). was an empire that controlled much of Southeastern Europe, Western Asia, and North Africa, Northern Africa between the 14th a ...
,
Muhammad Ali Muhammad Ali (; born Cassius Marcellus Clay Jr.; January 17, 1942 – June 3, 2016) was an American professional boxer, activist, entertainer, poet and philanthropist. Nicknamed The Greatest, he is widely regarded as one of the most significan ...
. When the British, after 1882, had to look after these structures generally referred to as ''barrages'', they adopted the term in their language and continued to use it for similar structures built by themselves across the Nile (Zefta Barrage and
Assiut Barrage The Assiut Barrage is a dam on the Nile, Nile River in the city of Asyut, Assiut in Upper Egypt (250 miles to the south of Cairo). It was completed in 1903. Background It was designed by the famous British engineer Sir William Willcocks who also ...
both completed in 1902). Since the British in the Egyptian Public Works Department kept close relations to their counterparts in
British India The Provinces of India, earlier Presidencies of British India and still earlier, Presidency towns, were the administrative divisions of British governance in the Indian subcontinent. Collectively, they have been called British India. In one ...

British India
, the term ''barrages'' made its way to present day India and Pakistan as well as to the Middle East, and thus generally into English.


See also

*
Diversion dam. This dam slows a normally fast and shallow river for partial diversion to a hydroelectric Hydroelectricity, or hydroelectric power, is electricity produced from hydropower Hydropower (from el, ὕδωρ, "water"), also known as water p ...
*
Weir A weir or low head dam is a barrier across the width of a river that alters the flow characteristics of water and usually results in a change in the height of the river level. They are also used to control the flow of water for outlets of lakes ...

Weir
* Head (hydrology) * the West Sea Barrage in North Korea


References


External links

{{Commons category, Barrages
Barrage
dictionary.com
Barrage
thefreedictionary.com Barrages (dam) Dams by type